In mid-April, a platoon of Chinese soldiers trooped some 20 km into territory considered India’s and pitched tents and unfurled banners. When detected by Indian forces, the Chinese refused to leave, triggering a tense three-week standoff between the two Asian giants that ended only after both sides backed down from their windswept Himalayan posts and returned to the pre-existing status quo. The incident was the most dramatic flare-up between India and China in recent years, the latest reminder of how things can heat up along a vast, snowbound border that has for decades remained in dispute.

Top officials in both New Delhi and Beijing tried to play down what happened. Indian Foreign Minister Salman Khurshid described the border tensions as “acne” on the otherwise “beautiful face” of Sino-Indian relations. On a recent trip to Beijing, Khurshid insisted both countries “were on the same page” and “don’t have prickly issues of significant difference” regarding the unsettled border. Ahead of newly installed Chinese Premier Li Keqiang’s May 19 visit to India — his maiden foreign mission — the two countries have made conciliatory noises over resolving the thorny issue of the border, even though over a dozen rounds of talks have failed to achieve any real progress. In a measure to build trust, the two countries laid plans during the standoff to hold joint military exercises for the first time in five years.

The Indian government described the incident as “localized,” which suggests that it was the fault of an errant Chinese official or local military commander, and not that of Beijing. Official talking points in both capitals tend to emphasize shared economic interests — annual bilateral trade is expected to reach $100 billion by 2015. Why should colonial-era quibbles over glaciers and desolate mountain passes get in the way?

But while the Indian and Chinese governments have grown accustomed to managing a conflict frozen on the roof of the world, a whole new terrain of contest is emerging far away from the Himalayas: the Indian Ocean. An Indian Defense Ministry report published last month warned of the “grave threat” posed by an emboldened Chinese navy in India’s maritime backyard. China’s rapidly expanding submarine fleet — it counts 45 such vessels to India’s 14 — has widened its orbit of patrols beyond Chinese territorial waters. The “implicit focus” of China’s navy, the report suggests, is to jockey for control of “highly sensitive sea lines of communication” in the Indian Ocean. Last year alone, the Indian Defense Ministry documented 22 “contacts” in the Indian Ocean with vessels suspected to be Chinese attack submarines on extended patrol.

These concerns add to an existing paranoia in the Indian media of China’s “string of pearls” — an array of ports, listening posts and naval bases that Beijing is supposedly setting up in countries around the Indian Ocean, ostensibly in a bid to encircle India. China has a stake in naval facilities in Burma, Bangladesh, the Seychelles, Sri Lanka and most notably in India’s old foe, Pakistan, where the Chinese-built port at Gwadar has furrowed many a brow in New Delhi. Chinese state companies are also developing key strategic ports in East Africa, including Lamu in Kenya and Bagamoyo in Tanzania. The day may not be too far off when a Chinese aircraft carrier makes routine pit stops at cities along the Indian Ocean littoral.

China’s naval presence in the Indian Ocean began in earnest in 2006, when Chinese vessels joined the international task force aimed at curbing Somali piracy in the Gulf of Aden and securing pivotal global shipping routes. Much of China’s booming economy is fueled by oil shipped from the Persian Gulf, through the Indian Ocean, and Beijing policymakers see the necessity of securing sea-lanes and access beyond the Strait of Malacca. It’s a typically realist posture, one which can be gleaned from the first ever Chinese “Blue Book” on India — a semiofficial policy document — published this month. It says New Delhi is preparing for the eventuality of a “two-front war” with China and Pakistan and notes the developing strength of India’s blue-water navy. It warns, as the Chinese often do, of the inherent instabilities of India’s democracy, which could lead to further tensions.

Many Indian strategists do seem to accept now that China’s widening naval scope is a natural consequence of its growing global presence; its expanding operations are that of any budding power seeking to safeguard far-flung economic interests. “There’s a maturation of Indian thought on the string of pearls,” says Jeff Smith, an expert on Sino-Indian relations at the American Foreign Policy Council in Washington. “Many recognize now that these are genuine [Chinese] commercial interests. The biggest reason India is also looking seaward is its own growth.”

But the parallel rise of China and India is still taking the world into uncharted waters. Theorists and analysts squint back at the era of Great Game rivalries, pointing to the now in-vogue writings of Alfred Thayer Mahan, a 19th century American naval officer and geostrategist who has become popular in both New Delhi and Beijing.

Mahan championed the need for a state to protect its merchant fleets with robust naval power — the blueprint for global domination used by the British Empire and later the U.S. But if China and India follow that same path, they’ll surely bump up against each other. Away from China’s expansion into the Indian Ocean, India has caused alarm in Beijing by stepping up its economic interests in the South China Sea and military ties with Vietnam, the main rival claimant to a body of water Beijing considers its sovereign territory. “Neither [India nor China] is really capable yet of operating in each other’s backyards,” says Smith. But the current course of action suggests further tensions may lie ahead.

In Samudra Manthan: Sino-Indian Rivalry in the Indo-Pacific, a book published in late 2012 by the Carnegie Endowment for International Peace, veteran Indian geopolitical analyst C. Raja Mohan deploys a parable from ancient Hindu mythology to explain the current strategic conundrum between China and India. Rival gods and demons churn the oceans in search of heavenly ambrosia, but the process yields poison. It takes the subtle interventions of the Lord Vishnu to first deal with the poison and then help manage the discovery of ambrosia.

In Raja Mohan’s metaphor, Vishnu ought to be interpreted as the U.S., still the dominant power in both the Indian and Pacific Oceans. But it remains unclear to what extent Washington, burdened with shrinking defense budgets and complex relationships with both China and India, could or would want to smooth out the hard edges of Sino-Indian competition. It’s certain that such a role would be unwelcome not just in Beijing, but also New Delhi, where policymakers have no desire to be drawn into the orbit of a Western superpower. And American ambivalence was on display last month as well. “Through the whole border dispute, there was not one word mentioned out of Washington,” says Smith. It’ll be up to Indian and Chinese politicos to make sure the geopolitical churn of the Indian Ocean doesn’t become poisonous.